The candidates aren't the only ones competing Tuesday: The pollsters, pundits and party chiefs who are paid to gauge, as accurately as possible, the country's political temperature have a lot riding on the results as well.
Here is a roundup of final predictions from some of those prognosticators:
• Larry Sabato, director of the University of Virginia Center for Politics, was one of the first to predict the Republicans would reclaim the House this year, and as the season has unfolded, he's moved more and more races into the Republican column.
The longtime political handicapper now has Republicans gaining 55 seats in the House and eight in the Senate, two short of the 10 needed to get to 51 seats and take control of the upper chamber.
"Ten [in the Senate] was always a stretch," he said.
He also has the Republicans picking up eight or nine governorships.
• Political analyst Charlie Cook says Republicans will gain 50 to 60 seats — and he says the wave could be larger.
"The midterm maelstrom pulling House Democrats under shows no signs of abating," he writes on his website, the Cook Political Report. "If anything, it has intensified."
Mr. Cook sees better prospects for Democrats in the Senate, calling for "a net gain for Republicans of 6 to 8 seats, down from 7 to 9 seats."
"While it is becoming increasingly likely is that Republicans will hold all 18 of their own seats," he writes, "Democrats' prospects in three of their 19 seats have improved in recent days. Sens. Barbara Boxer in California and Patty Murray in Washington now appear to be headed for re-election, albeit by small margins. In the special election in West Virginia, Democratic Gov. Joe Manchin now holds an advantage."
Among governors, Mr. Cook has the GOP with a "6 to 8 seat net gain."
• Analyst Stuart Rothenberg said Democrats face a "potential bloodbath."
The founder of the Rothenberg Report predicts six to eight new seats for the GOP in the Senate and a whopping 55 to 65 in the House.
There are, however, some observers who remain unconvinced — at least publicly — that the Republican wave will be a tsunami.
"I have the Republicans picking up 45 House seats but losing four for a net gain of 41 seats, which is lower than most people," says Ken Rudin, NPR political director. He joked on the air last week that "I guess the reason is because NPR is liberal, and that's why we're rooting for the Democrats."
He had the Republicans picking up seven in the Senate.
• Real Clear Politics projects Republican pickups of eight Senate seats and six governorships, though the popular online survey aggregator holds out a thin reed for Republicans hoping to take control of the Senate, which an 8-seat pickup won't do.
As of Sunday afternoon, Real Clear Politics had Democrats ahead 48 seats to 45 (counting those not up for re-election), with seven races still ranked as tossups.
In the House, Real Clear Politics had Republicans winning 221 seats to the Democrats' 171, with 43 seats rated tossups. Even if the Democrats won every one of those close elections — an unlikely scenario — the Republicans would have more than the 218 seats needed to form a majority.
Blaming his party's woes on "poor communications," outgoing Pennsylvania Gov. Edward G. Rendell on CBS' "Face the Nation" conceded Sunday that Democrats may lose the House, but he said the party's problems are overstated.
"I'm not saying we're necessarily going to hold onto the House, but I think there are going to be some surprises on Election Day," he told host Bob Schieffer.
Rep. Chris Van Hollen, whose job as chairman of the Democratic Congressional Campaign Committee is to get Democrats elected, remains confident. "It's not a lost cause," the Maryland congressman told host Chris Wallace of Fox News on Sunday. "All these Washington pundits are going to be surprised - I believe Democrats are going to hold on to the House."
And Democratic National Committee Chairman Tim Kaine doubled down on Mr. Van Hollen's optimism. The former Virginia governor, appearing Sunday on NBC's "Meet the Press," said Democrats will hold both the Senate and the House. "I'm not going to predict, but I believe we will hold both houses."
Still, the overwhelmingly verdict is that Tuesday will belong to the Republicans.
John Fortier of the American Enterprise Institute has the Republicans picking up 45 to 50 seats.
Syndicated columnist Charles Krauthammer predicts a House gain of 55 seats and eight more seats for the GOP in the Senate.
Republican strategist Grover Norquist, president of Americans for Tax Reform, told the National Interest that Republicans could win 50 or even 51 seats in the Senate, but predicted the final total would be "more likely 47 or 48."
Pollster Mark Penn, who heads up Penn Schoen Berland, has the Republicans gaining around 50 in the House. "It's fair to say that Democrats will be devastated in the South," the former adviser to Hillary Rodham Clinton told "The Hill."
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